With recent tendencies toward electronic apparatus becoming not only of higher performance but also compact and portable, electronic components used therein are becoming more compact and of higher performance. Particularly, a capacitor for use in an output smoothing circuit section of a power supply is required to assume low impedance and low equivalent series resistance (ESR) in a high frequency band.
A solid electrolytic capacitor, which uses a conducting polymer as electrolyte, can be made into a compact large-capacitance capacitor of low impedance and low ESR through stacking of monolayer capacitor elements. Various solid electrolytic capacitors of this type have been proposed.
A conventionally proposed method for producing monolayer capacitor elements for use in a solid electrolytic capacitor includes the steps of forming, through blanking, a comb-like blank from wide metal foil, the comb-like blank including a support portion and a plurality of protrusions, which will be used as capacitor elements; processing the protrusions after the support portion is fixed on, for example, a rest plate; cutting the processed protrusions from the support portion; and stacking the cut pieces (Japanese Patent Application Laid-Open (kokai) No. 5-166681). Another proposed method includes the steps of forming metal foil into a blank assuming a predetermined shape through, for example, photoetching; obtaining monolayer capacitor element from the blank; and stacking the monolayer capacitor element (Japanese Patent Application Laid-Open (kokai) No. 9-36003). However, these methods have the problems of insufficient economy and low production efficiency.
In order to solve the problems of the conventional production methods, the present inventors, among others, have proposed a method which repeats the steps of connecting elongated tape-like metal foil to a side edge of a metal plate or metal wire (guide member) perpendicularly to the length direction of the guide member and cutting the metal foil to a predetermined length, to thereby form a comb-like member including the guide member and a plurality of metal foil pieces bonded, in parallel to one another, to the guide member and which further includes the steps of forming sequentially on the surface of each of the metal foil pieces a dielectric oxide film layer, a semiconductor layer, and a conductor layer and separating the metal foil pieces from the guide member for use as solid electrolytic capacitor elements (Japanese Patent Application Laid-Open (kokai) No. 4-17318 (Japanese Patent No. 2828317)). This method can produce a solid electrolytic capacitor element efficiently at low cost.
The present invention relates to a production apparatus for carrying out, at good productivity, the previously proposed production method mentioned above and provides an apparatus for producing, at good productivity, a comb-like capacitor element member including a metallic guide (guide member) and rectangular metal foil pieces, each serving as valve metal, bonded to the guide member. In production, mere shearing of metal foil tends to cause generation of burrs or cracks on the cut surface of a resultant metal foil piece, thus damaging the metal foil piece. Such damage to the foil impairs characteristics of a monolayer capacitor element, thus impairing efficiency in production of a solid electrolyte capacitor, particularly a solid electrolyte multilayer capacitor. Thus, a production apparatus of the present invention employs a preferred cutting mechanism in which, after cutting, cutting blades retreat from the cutting position while maintaining a clearance therebetween, to thereby suppress generation of burrs and cracks. When an electrode of a welding machine becomes dirty during welding of metal foil, continuous welding becomes difficult to attain; therefore, the production apparatus of the present invention employs an automatic polishing mechanism for polishing the electrode to thereby enable continuous and accurate bonding of metal foil.
The present invention further provides an automatic feed apparatus equipped with a constant-length feed mechanism for automatically feeding an elongated tape-like metal foil by a constant length for carrying out, at good productivity, the previously proposed production method mentioned above. Since the elongated tape-like metal foil is thin, the foil is easily torn or broken, and the foil surface is damaged easily. Therefore, the present invention also provides an automatic metal-foil feed apparatus, which is preferably equipped with means for preventing breakage of the foil and damage to the foil surface and which can draw the elongated tape-like metal foil from a reel and feed the metal foil by a constant length every feeding operation, with high positional accuracy and without damaging or deforming the metal foil, in a process for bonding a plurality of pieces of the metal foil to a metallic guide.
Further, the present invention provides an apparatus and a method for cutting an elongated tape-like metal foil which is used in an apparatus for producing a capacitor element member. Conventionally, a capacitor element sheet is cut by use of a cutter or dicing saw (Japanese Patent Application Laid-Open (kokai) No. 09-260218) or by use of a laser beam (Japanese Patent Application Laid-Open (kokai) No. 05-299309) in order to produce capacitor elements. However, cutting by use of a cutter or dicing saw causes deformation of cut surfaces, such as sagging and cracks, and imparts great damage to the cut surfaces, such as exfoliation of an etching layer of a metal foil (dielectric body layer). Such damage to foil causes a deterioration in the properties of monolayer capacitor elements, and production efficiency of solid electrolyte multilayer capacitors decreases. When cutting is performed by use of a laser, the damage to cut surfaces is relatively small. However, production cost becomes high due to high facility cost, and the size of the facility increases.
The present invention provides a cutting apparatus and method which do not impart such damage to metal foil and hardly produce burrs, cracks, or deformation on cut surfaces.